Hydraulic power unit



' Feb. 25, 1947. M, MATHYs 2,416,339

HYDRAULIC POWER UNIT I Filed Feb. 17, 1941 6 Sheets-Sheet 1 7720A: A.mat/23$ Feb. 25, 1947, M. A. MATHYS 2,416,339

HYDRAULIC rowan Unn- Filed Feb. 17, 1941 6 Sheets-Sheet 6 59 i max A.7724172516 M'T ws Patented Feb. 25. 1947 2,416,339 Q UNITED STATESPATENT OFFICE HYDRAULIC POWER UNIT Max A. Mathys, Detroit, Mich,asslgnor to Ex- Cell-O Corporation, Detroit, Mich., a corporation ofMichigan Application February 17, 1941, Serial No. 379,211

22 Claims. 1

The present invention relates enerally to imrovements in hydraulic powerunits, and has particular reference to such unit having a spindiemounted for rotation and'axial translation, and having self-containedmeans for driving the spindle and for translating the spindleautomatically through a predetermined program of movements, such forexample, as a cycle comprising a rapid approach, a forward feed, and arapid return. v

One of the objects of the invention is to provide a novel hydraulicpower unit which is simple, compact and sturdy in construction and whichis extremely powerful, rapid, eflicient and silent in operation. a

Another object is to provide a new and improved power unit embodying ahydraulic actuating system capable of utilizing extremely high pressureswithout resulting in excessive heat.

A further object is to provide a novel hydraulic power unit which isadapted to maintain a uniform adjustedrate of feed regardless ofvariations in resistance.

A more specific object is to provide a new and improved power unitembodying a variable delivery pump, and an orifice control foreffectinga uniform rate of feed uninfluenced by changes in the pumpdelivery pressure.

Still another object is to provide a power unit embodying a novelhydraulic system for translating the spindle, which system utilizesrelatively high working pressures so as to minimize irregularities andinaccuracies in the feed movement automatically caused by the presenceof entrained air or vapor in the motive fluid, and

consequently to obtain a uniform rate of feed regardless of varyingresistance to the movement of the actuator. 4

A further object is to provide a new and imroved hydraulic power unit inwhich the component elements, such as the pump, the valves.

and the actuator are so correlated that leakage is automaticallycompensated for and not reflected in the feed movement of the actuatorunder varying load conditions.

Another object is to provide a power unit having novel means forcontrolling the operation of a power unit embodying the features of myinvention. a

. Fig. 2 is a fragmentary front side elevational view of the power unit,partially sectioned along line 22 of Fig. 1. v

Fig. 3 is a longitudinal vertical sectional view of the power unit takensubstantially along-line 3-3 of Fig. 1.

Fig. 4 is a fragmentary transverse vertical sectional view takensubstantially along line 4-4 of Fig. 3, and illustrating the controlvalve.

Fig. 5 is a fragmentary sectional view taken substantially along line 55of Fig. 4.

Fig. 9 is a plan-development of the periphery of the control valve.

Fig. 10 is a diagrammatic representation of the hydraulic controlcircuit of the power unit.

Fig. 10a is a fragmentary view of a modified form of pump control lineadapted for use in the circuit.

Figs. 11a to 11c are aset of fragmentary transverse sectional v'ewsillustrating the adjustment of different axia y spaced portions of thecontrol valvewhen the latter is in stop position.

Figs. 12a to 12c are corresponding views of the control valve in rapidapproach position.

Figs. 13a to '13s are corresponding views of the control valve inforward feed position.

Figs. 14a to lie 'are corresponding views of the control valve inreverse or rapid return position. Figs. 15 and 16 are views of the pumpvalve taken respectively in the directions of the arrows the spindleactuator automatically, and having a single manual control operablewithin the limits of the automatic range without likelihood of injury tothe structure.

Further objects and advantages will 'become.

apparent as the description proceeds.

In the accompanying drawings, Figure 1 is a forward end elevational viewof l5l5 and l6-l6 of Fig. 3.

Fig. 17 is a fragmentary sectional view of the control valve taken alongline ll-ll of Fig. 4.

Referring more particularly to the drawings,

the power unit constituting the exemplary embodiment of the inventioncomprises a hollow housing I adapted to be mounted in fixed position ona suitable support (not shown). The housing 1 preferably is generallyrectangular in shape, longitudinally and transversely. A mounting baseor plate 2 is integral with the bottom of the housing I, and is formedwith a central longitudinallocating groove 3.

The housing'l has an internal space, the lower portion of whichconstitutes an enclosed liquid reservoir 4, and is formed in the forwardend over the reservoir with an internal solid body structure 5. A coverplate 6 is removably secured t the forward end of the housing. I, andserves to lose one end of the interior. Bimilarly, the other end of thehousing I is closed by a removable gear case 1 having a cover plate 8.

A longitudinal spindle 9 is mounted for rotation and axial reciprocationinthe housing I, and projects from the forward end thereof forattachment of a suitable tool or workpiece. To support the spindle 9, atubular quill It! extends through, and is mounted for reciprocation in,a cylinder ll formed in the body structure 5. Two

flanged heads or bushings I 2- and I3 are rigidly secured to oppositeends of the body structure 6 to close the cylinder II, and serve asguides for opposite end portions of the quill III. The quill I is formedintermediate its ends with a piston l4 slidably disposed in the cylinderH, and the opposite endportions of the quill therefore c'onstitutepiston rods. In the present instance, the

piston I4 is of the differential type, with the rear area approximatelyequal to twice the forward area.

The forward end of the quill l0 extends from the cylinder head 1 l2through an alined opening or bore in the cover plate 6. A sleeve I6 isfitted in the bore 15, and is formed at its inner end with an externalperipheral flange l1 seated in a counterbore I 8, and at its outer endwith an internal peripheral flange l9 in wiping engagement with thequill III to prevent the entry of chips and other foreign matter. Thecylinder head I2 is seated in a counterbore in the ini, ner end of thesleeve l6. Consequently, the cover plate 6 serves to maintain thecylinder head I2 and the sleeve l6 both tightly in position. An oil seal2| is confined within the sleeve l6 in wiping engagement with the quilll0. Any fluid reaching the sleeve I6 is returned through a passage 22 tothe reservoir 4 within the housing I. A tubular bearing housing 23 hasan internal flange 24 at one end secured coaxially to the quill Ill. Thespindle 9 extends in peripherally spaced 3 relation through the quilllll' thereby defining an intervening clearance space 25, and projectsthrough the flange 24. The forward end of the spindle 9 is'formed withan-enlarged nose 26 which projects from the bearing housing 23, and

which is suitably supported therein by a radial and end thrustanti-friction bearing 21. More particularly, the inner raceway of thebearing 21 i -is confined on the spindle nose 26 against an inj wardlyfacing annular shoulder 29 by an annu-' lar nut 29, and the outerraceway isconfined in 1 a counterbore 30 in the housing 23 by an annularnut 3|. The bearing 21 is closed from the exterior by a washer 32 andoil seal 33 secured in Consequently. the spinis connected for axialmovement therewith.

Formed in, and opening to, the outer end of the spindle nose 26 is anaxial bore 34 adapted to receive a removable socket member 35. In thepresent instance, the member 35 is formed with 1 a, conventional tapersocket '36 adapted to receive the shank of a tool (not shown). member 35may be adjusted axially within the spindle nose 26 by means of a nut 31to compensate for tool wear, a spline key 38 serving to con- The socketSuch head would have an operative drive connec- 1 tion with the spindle9 through the bore 34.

The rear or inner end of the spindle 9 is longitudinally splined forindependent axial movement relative to a rotary drive sleeve 43journaled in the gear case I. More particularly, this 15 sleeve 43 ismounted in spaced anti-friction ball bearings 44 supported respectivelyin the gear case I proper and the cover 8. The inner end of the quill 10in its rearward-position telescopes freely with the contiguous end ofthe spline sleeve 43, 20 and is open to the interior of the housing I.It may be mentioned at this time that any liquid tending to leak pastthe piston M in the cylinder H, from one side to the other, will beintercepted by a peripheral drain groove 45 open- 25 ing through radialpassages 46 in the piston to the clearance space 25, and from there willdrain through the inner end portion ofthe quill ID to the reservoir 4.The path of drainage to the reservoir 4 is represented schematically inFig. 10

so by the catch pan 4 and the line 4 The rotary drive for the spindle9comprises a gear 41 removably keyed to the spline sleeve 43 between thebearings 44. Meshing with the gear 41 is a gear 48 removably keyed'to adrive shaft 95 4'9 journaled in spaced anti-friction bearings 50 mountedrespectively in the gear case vI proper and the cover 8. The shaft 49extends through the gear case to the exterior of the housing I, and apulley 5| adapted to be connected to a suitable source of power (notshown) is fixed on the outer end. The gears 41 and are located within arecess 52 in the outer face of the case I proper, and may be changed,upon removal of the cover 8, to obtain different selected speed ratiosin the spindle drive from the power input shaft 49.

A hydraulic system (Fig. 10) is incorporated in the power unit fortranslatingthe spindle 9 ax-' ially through a predetermined program ofmovements. While different cycles may be employed,

an illustrative cycle comprises rapid I approach from the stop position,forward feed. automatic reverse, and rapid return to the stop position.

' Optionally, a dwell may be provided at the end of the forward feedlandbefore reverse. In the present system, the rate of feed and the periodof dwell are subject to accurate adjustment and control.

The hydraulic system, in its preferred form," 60 comprises generally avariable delivery pump 53 driven at a constantspeed by the shaft 49, Thepump 53 has an inlet line 54 taking fiuid from the reservoir or sump 4,andv a discharge line 55 for supplying fluid under pressure. A controlvalve 56 is operable to connect the pressure line 55 selectively to twosupply lines- 51 and 58 leading to opposite ends of the cylinder II, andalso The pump (Figs. 3 and a) shown in the drawings, is of the typehaving parallel annularlyarranged piston and cylinder units, and ismounted on the inside of the gear case 1 within the housing I. In itspreferred form, the pump 58 comprises a stationary valve member 88 and arotarycylinder body 8|, having flat annular end the cylinder body 5|.Formed in the bore 88 are internal splines 58 which interflt slidablywith longitudinal splines I8 on the inner end of the shaft 4-8 toestablish the drive connection for the pump 53, and which are relativelyshort so as to permit a limited amount of peripheral float of thecylinder body 8| and thereby insure accurate seating of the valve faces52 and 53,

Formed in the cylinder body 5| in parallel uniformly spaced relationabout the bore 58 are a the other end is closed to define a pressurechamplurality of pump cylinders H having cylinder ports 12 opening fromthe inner ends to the valve face 83. Suitable pump pistons or plungers18 are respectively reciprocable in the cylinders II. The plungers 13are urged outwardly by coiled compression springs 14. These springsengage the inner ends of the cylinders II, and extend into bores I5 inthe inner ends of the plungers 18 so that the latter may becomparatively short in length.

A swash plate I8 having a flat bearing face I1 is in operativeassociation with the outer ends of the plungers l3, and when inclined isadapted to cause reciprocation of the plungers in uniformly timedsequence upon rotation of the.

cylinder body 5|. Bearing shoes 18 are connected by means of suitableinserts I8, for universal pivotal adjustment, to the outer ends of theplungersl3, and have flat faces in sliding engagement with the bearingface 11 of the swash plate 18., The swash plate 15 is mounted in thehousing I on a pivot pin 88 atone end for angular adjustment about anaxis extending transversely of the axis of rotation of the cylinder body8i. point adjacent the axis of each plunger 18- as the latter reachestop dead center position at the end of the pressure stroke. As a result,the

' plate I6 is adjusted into a plane perpendicular to the shaft 48, noreciprocation will be imparted to the plungers 18- and the pumpdisplacement will be zero. In the reciprocation of the plungers 13,those on the suction stroke take in fluid from the line 54, and those onthe pressure stroke discharge fluid to the line 55. For further detailsof the pump valve porting, reference may be had to a copendingapplication, Serial No. 348,904,.iiled July 31, 1940', by Ira J. Snaderand Max A. Mathys (now Patent'No. 2,299,235, issued October 20, 1942) aa 15 to level off the latter.

Preferably, the pin 88 is located at a- 50 a c v The swash plate 18 isangularly adjustable about the pin 88 to vary the displacement of thepump. Within the broad aspects of the present invention, such adjustmentmay be effected 5 by any suitable means. In the present instance,

10 control pressure. and to increase the delivery upon a decrease in thepressure. The particular means for this purpose comprises a balancingplunger 8| and a control plunger 82 acting on the free end of the swashplate I8 in a direction The balancing plunger 8! establishes a conditionof balance against the v hydraulic reaction-in the cylinder II, andinthe s plate into its maximum stroke position.

The pressure balancing plunger 8! (Fig. 8) isv reciprocable in a bore 88formed in the body structure 5 of the housing and extending transverselyofthe pin 80. One end of the bore 88 opens toward the free end of swashplate 15, and

-ber 84 and is connected through a branch line 85 to the pressure line55 of the pump 53. A shoe 88 is connected by means of an insert 8'! for6 universal pivotal adjustment to the outer end of the plunger 8|, andbears s'lidably against a fiat face 88 on the rear of the swash plate16. The diameter of the plunger 8| and the moment arm of force exertedthereby on the swash plate 15 are such that this force willsubstantiallycounterbalance the hydraulic reaction in the pump cylinders II. Sincethe delivery pressure ofthe pump 53 is always connected through thelines 55 and 85 to the pressure chamber 84 at the inner end of theplunger 8|, the swash plate 15 structure 5 of the housing I and openingtransversely of the pin 88 to the rearface 88 of the swash plate I8. Ashoe 80 is connected by means of a suitable insert 8| (Fig. 3) foruniversal pivotal adjustment to the outer end of the plunger 82, andslidably engages the face 88. A positive stop is provided to limit theposition of maximum inclination of the swash plate 15 which determinesthe maximum pump delivery. In the present instance, this stop consistsof a plug 5 82 positioned in the inner end of the bore 88 for engagementby the plunger 82. Opening from the innerendof the bore 88, between theplunger 82 and the plug 82, is a pump control line 83. This linemay beconnected to any suitable source of control pressure, and in the presentinstance is adapted to be connected by the control valve 58 to theexhaust side of the cylinder ll so as to utilize the back pressure underorifice control .70 versely through the body structure 5 of the housingl, and a valve plug 85 mounted for rotary adjustment therein. It will beunderstood that the various lines or passages 55, 51, 58, 58 and 88 haveappropriate port openings to the periphcry of the valve bore 84. Thevalve 58 may be In the present mg to the bore I I3.

constructed to provide any desired program of d v axial movementsof thespindle 9, and in the present instance is of the four-position type,defining a cycle comprising rapid approach, forwar feed, reverse, rapidreturn' and stop. I

' r In its preferred construction, the valve plug 96 is formed in onetransverse plane b-b (Figs. 4.

y 8 I posite sides of the grooves I26 and open to the peripheral groovesI94 and I95. The grooves I21 preventleakage from the pressure ports I99and I9I and the groove II9 to the groove I26, so that variations in thepump pressure will not be refiected in the rate offeed as controlled bythe orifice I25. It will be understood that theeffective flow area ofthe orifice I is controlled by the position of the tapered notch I23,and is progressively reduced upon rotary adjustment or the plug II4 tomove in a direction of decreasing lateral area across the orifice.

Assuming that the spindle 9 is in retracted stop position, the controlvalve 58 'willoccupy the position shown in Figs. 11b, 11c and 11d. Inthis position of the valve, the line 51 to the forward ripherally spacedradial ports I99, I9I and I92 opening to the pressure bore 99, and henceconstituting pressure ports. The outer end of the 'port I92 isperipherally elongated as indicated at I93.

The cylinder lines 51 and 58 open at diametrically opposite points tothe bore 94 in the plane of the ports I99, I9I and I92. Also formed inthe plug 95 are two axially spaced peripheral exhaust groove I94 and I95which are interconnected by two peripherally spaced longitudinal groovesI9, termediate t epressure ports I9I and I92, 'and 3 102 and I99. Theexhaust line 59 opens to the bore 94 in the plane of the groove I95. Twoadditional longitudinal exhaust grooves I98 and I99 are formed in theplug 95 respectively between the notches 98' and 91, and open to theperipheral roove I94.

v The pump control line 93- opens to the periphery of the valve bore 94in a transverse plane d-d (Figs. 4, 9, 11d, 12d, 13d and 14d). Formed inthe periphery of the plug 95 is a longitudinally inclined pressuregroove II9 which extends from the pressure port I9I to the plane d-d,and two short'longitudinal exhaust grooves III and H2 which extend fromthe peripheral exhaust groove I95 through the plane d-d, and which areapproximately in alignment with the ports I9I and I99.

Formed in one end of the valve plug 95 is an axial orifice valve bore II3. An orifice valve plug nd I 91 located respectively inend of thecylinder II is blocked, the line 58 from the other end of the cylinderis connected through I9I-I95 to the exhaust line 59, and the pumpcontrol line 93 is connected through II9--I9I- 99999'| to the pressureline 55 of the pump 53. The pressure in the line 93 causes the swashplate 16 to level ofi into no-delivery position so that the pump servesonly to maintain a constant low pressure in the line 55 equal to thepressure in the line 93. a

Upon adjustment of the valve 56 in a counterclockwise direction (Figs.12b, 12c, and 12d) into H4 is secured by means of a flat key II5 forrotary adjustment in the bore H3, and has an actuating shaft I I6 formedwith 'an adjusting dial III disposed against the outer end of thecontrol valve plug 95.' If desired, a spring washer I I8 may beinterposed between the plug 95 and the dial II'I-to take up lost motionand to provide a frictional retaining means. is slotted to receive asuitable hand tool for rotatably adjusting the plug H4, and isappropriately graduated to indicate theselected feed adjustment.

' Theorifice valve plug I I4 is formed with an axial bore I I9 whichopens through a radial port I 29 to a peripheral groove I 2| in turnconnected The dial I IT through a radial port I22 in the plug 95 to theperipheral exhaust groove I95. Also formed in the plug H4 is a taperedperipheral notch I23 which is connected at its large end through aradial port I24 to the bore H9; and which is rotatably adjustable acrossan orifice I25 open- I25 opens to a longitudin'algroove I28 formed inplanes 0-0 and dd. Suitable small drain V- grooves I21 are formed in theplug 95 along op- The outer end of the orificerapid approach position,both cylinder lines 51 and 58 are connected through I99-I92-99-98 to thepressure line 55, and the pump control line 93 is connected throughIl2-I95 to the exhaust line 59. Consequently, the swash plate I6 isadjusted by the springs 14 into maximum delivery position as determinedbythe stop 92.

Because of the difierential area of the piston I4, fluid displaced fromthe front end of the c linder II is directed to the large end of the clinder. The rapid approach, therefore, occurs at a maximum rate ofspeed.

Upon subsequent adjustment of the valve 56 in a clockwise direction intoforward feed position (Figs. 13b, 13c and 13d),'the line 58 is connectedthrough I93--I9299-989'| to the pressure line 55,.the line 5'! isconnected through I26-the orifice I25I23-I2 4-II9 I29I2I I22-I95 to theexhaust line 59, and the pump control line 93 likewise is connected tothe groove I26 at the inlet side of the orifice. Consequently,

the orifice I23 meters the fluid discharging from the forward end of thecylinder II, and the back pressure thus created is utilized to reduceand control the discharge of the pump 53 to the desired uniform feedrate.

At the end of the forward feed, the control valve 56 is. reversed (Figs.14b, 14c and 14d) to effect a rapid return of the spindle 9 into initialstop position. In this condition of adjustment of the valve 56, the line51 to the forward end of the cylinder I I is connected through I9I-99.98-91 to the. pressure line 55, the line 58 from the rear end of thecylinder is connected through I Ill-I95 directly to the exhaust line 59,and the pump control line 98 is connected through III- I95 to theexhaust line 59'. Consequently, the

clusion of both plunger 8| and 82. in thediagrammatic disclosure, thepump 53 has been shown in the position of zero displacement. In 9 theactual construction, the plungers 8I and 82 are disposed side by side atthe same distance I from the pivotal axis of the swash plate I6 and formaximum displacement the swash plate aerasse would occupy a position ofmaximum inclination. 7

Since the rear area of the piston I I is twice as large as the forwardarea, and since in rapid approach the opposite ends of the cylinder areinterconnected, the rapid return and the rapid approach will have thesame rate of movement.

The orifice control in the exhaust side of, the hydraulic system sets upa back pressure which is utilized to control the displacement of thevariable delivery pump during feed operation. This stantially at zerodisplacement, but does supply fluid to maintain the system under lowpressure. During feed condition, the control pressure and the springpressure are in sensitive balance. The foregoing arrangement servesideally to dampen any pressure pulsation tending to occur. Thus,

the opening pressure imparted to the swash plate 16 by the springs 14 iscomparatively light, and

a momentary closing pressureimpulse is com-. paratively high.Consequently, one side of the harmonic pulsation curve is slowed down,although the action is so rapid that it is not discernible to the eye,thereby resulting in eflective dampening.

The pump delivery pressure will vary over a wide range, depending on thework resistance, and onoccasion may be extremely high. However, thepressure for regulating the pump .53 during feed operation, beingindependent of the pump delivery pressure, is relatively constant,

' and may be comparatively low and much less than'the maximumpump-pressure. The low control pressure is advantageous since less heatwill be generated in the passage of fluid through the orifice than if ahigh pressure were employed.

Also, pulsations are more eflectively eliminated with the use of a lowcontrol pressure. While a comparatively low control pressure isdesirable, it should be sufliciently high to avoid substantial changesin the compressibility of the fluid. I have found that in the presentinstallation, a sensitive control is obtained when the back pressurecreated by the orifice is maintained above 110 pounds per square inch.The most suitable orifice pressure and hence the pump control pressurecan be determined from the compressibility curve of the motive fluid foreach installation. In a typical curve, the compressibility initiallyincreases rapidly with an increase in pressure, and then levels oil. andincreases only slightly as the pressure continues to increase over asubstantial range. If the pressure is selected In this range where thecompressibility of the fluid is fairly uniform, the control of the pumpwill have a low elasticity. regardless of loadv variations, changes infiuid viscosity, the presence of entrained vapors and pressurevibrations in the system.

- The valve plug 35 is confined in the bore 94 against endwise movementand for rotary adjustment. To this end, a collar I28 is removably keyedon one end of the valve plug 95 for rotation therewith, and is rotatablewithin-a counterbore I29 in one end of the valve bore 34. A hand knobI30 isflxedtotheextremeendotthevailveplug 95 at the front of the housingI and serves to confine the collar I23 in position, and as a means foradjusting the valve 58 manually. A collar I3I is keyed to the other endof the valve plug 95 and is rotatably confined in a counterbore I32. Thecollar I3I is held in position by an abutting collar I33 fixed on theextreme and of the plug 95. It will be seen that the valve plug 35 andthe collars I28 and I3I are confined in bled relation within the bore 34by the hand knob I33 and the collar I33. The extreme ends of the valveplug 95 are of the same diameter so that the hand knob I30 and thecollar I33 may be interchanged if it should be desired to adjust thevalve manually from the other side of the housing I.

To provide means for adjusting the valve 55 in timed relation to theaxial movements of the spindle 9, a dog bar I34 is connected at itsforward end by a pin I35 to theiiange or faceplate 40 of the housing 23.The pin I35 is rigi y threaded into the dog bar I34 and has an accuratesliding fit with a radial bore I35 in the face plate 40. The bar I34extends slidably through a hole I31 in the front cover 5 and an alinedhole I38 formed in the side of the housing I, and is therein supportedto provide a slight clearance I33 between the bar and the face plate 43.The loose connection between the dog bar I34 and the face plate 40serves to maintain the quill II securely against angular displacementwithout requiring close accuracy in alinement.

Formedin the bar I34 is a longitudinal groove I 40 for adjustablysupporting a plurality of valve control dogs. In the present instance,three dogs are shown, namely, a stop dog I, a feed dog I42, and areversing dog I43. To support the dogs, the longitudinal groove I43 isformed with three accurate faces I44; I45 and I45. Suitable clampingscrews I41 are threaded through each dog into engagement with the barI34 opposite the face I46. The clamping pressure is mainly absorbed bythe face I46 and comparatively small pressures are absorbed by the facesI44 and I45. Consequently, the main pressure is absorbed longitudinallyof the screws I41 so that even with a large clamping pressure, nosubstantial bending force is imparted to the dog bar. Although more thanhalf of the dog bar is cut away, the bar affords a rigid support for thedogs and retains a good sliding fit in the bores I31 and I33.

The dogs "1,": and m are arranged m selective engagement with dogabutments I45, I49 and I50 on the collar I23. These abutments are spacedaxially of the collar I 23 to avoid interference, and are movablesuccessively into position for engagement by the respectivedogs.

Coacting with the dog control is a spring reversing mechanism. In itspreferred form, this mechanism comprises the collar I3I which isslidably disposed respectively in bores I55 and I55,-

opening tangentially to opposite sides of the valve bore 94, and areadapted for engagement with the ward movements.

. v 1 11 to hold the abutment I48 against the stop dog -I4I (Fig. 11a)in stop position.

' To start the cycle, the valve 56 is rotated in a.

counter-clockwise direction, for example by means of the hand knob I30,thereby forcing the plungers I 53 and I54 (Fig. 12a), and moving theabutment I49 into the path of the feed dog I42 (Fig. 12e). Inthisposition, the plungers I53 and I54 engage the periphery of the reversecollar I3I, and hence are ineffective. The ;valve 56 is now in positionto effect the'rapid approach movement of the spindle 9.

At the end of the forward approach movement,

the feed dog I42, which travels with the quill I0, engages the abutmentI49 to rotate the-valve 56 clockwise througha predetermined angle intothe 4 forward feed position. As a result, the abutment I50 is moved intothe path of the reverse dog I43 (Fig- 13e), but, the plungers I53 andI54 still remain in engagement with the periphery of the collar I3I(Fig. 13a). The spindle 9 now moves as a feed rate determined by thesetting of the" adjustable groove I23.

At the end of the feed movement, the reverse dog I43 engages theabutment I59 to rotate the effect the rapid return movement of thespindle 9 into the initial stop position.

-At the end of the rapid-return, the stop dog I4I engages the abutmentto rotate the valve 56 counter-clockwise against the spring action ofthe plungers I53 and I54 into the stop position (Figs. 11a and 11c).

Instead of reversing the valve 56 immediately at the end of theforwardfeed, a dwell may be interposed before reversal. Such dwell isobtained by means, of a valve reversing mechanism having a. time delay.To render such dwell mechanisms functionally operative, the reverse dogI43 is removed, and the quill I9 is caused to engage a positive stop atthe end. of the for In the present instance, the forward end of thecylinder I I, upon engagement with the piston I4, serves as the stop.

The dwell mechanism (Figs. 4, 5, 7 and comprises a tubular or hollowfloating plunger I56 reciprocable in a, bore I60 formed in the bodystructure 50f the housing I and transversely intersecting the main valvebore 94. A gear I6I rigid with the valve plug 95 meshes with alongitudinal gear rack I62 formed in the side of the plunger I59. Therange of the reciprocation of f the plunger I59 is suitably limited by astop plug 1 I63 removably, inserted in-one end of the bore I60, and anactuating piston I64 slidable in a cylinder bore I65 opening to theother end of the bore I60. The actuating piston I64 has a head I66defining its retracted position, and is movable inwardly against thecontiguous end of the plunger I 59 to shift the latter, together withthe plungers I53 and I54, into one end position in engagement 1 i withthe stop plug I63, and thereby to locate.

the'control valve 56 in reverse position; Move- I ment of the plungerI59 into the other end position against thepiston I64 when the latter is35 to the orifice.

The closed end of the cylinder bore I65 is connected through a line I61to a dwell and relief valve I68 (Figs. '1 and 10). This valve comprisesa sleeve I69 fixed in a bore I10 in the gear case 5 1, and having anaxial bore "I open at one end to a drain line I12 leading to thereservoir 4. Threaded into the other end of the bore I10 is a closedtubular cap I13 connected to a branch,

of the drain line I12. A valve plunger I 14 is 10 reciprocable in thebore "I; and has a stopflange I normally urged into engagement with theinner end of the sleeve I69 by a coil compression spring I16confinedwithin the cap I 13.

Two spaced'annular grooves I11 and I18 are 15 formed in the outerperiphery of the sleeve I69,

and open respectively through radial ports I19 and I80 to the bore I1I.nected respectively to the pressure line 55 and the line I 61. Formed inthe periphery of the valve plunger I14 aretwo axially spaced grooves I8Iand I82 movable selectively into registration with the ports I80.Suitable openings I83 are formed in the-flange I15 connecting the grooveI I82 to the interior of the cap I13.

The valve plunger I14 is formed in one end portion with an axial boreI84. The outer end of this bore is closed by a screw plug I85, and theinner end is connected through a passage I86 open to the port I19. Anorifice plug I81, with a restricted axial orifice I88 in one end wall,is

removably threaded into the inner end of the bore I84 and is spaced fromthe plug I85 so that the middle portion of the bore defines a confinedspace open to the interior of the plug and hence The intermediateportion of the bore I84, at the downstream side of the orifice I88 isconnected through a 'passagel89 in the I plunger I14 to the groove IBI.

' The inner end of the bore I'II opening to the 0 line I12 is reduced indiameter to define a relief valve passage I90, and the corresponding endof the valve plunger I 14 is reduced in size to constitute a reliefvalve memberJSI. slidable in the passage. Hence, the plunger I19 isformed with a pressure face I92 open to the ports I 19. Suitable taperedgrooves I93 are formed in the periphery of the valve member I 9! formovement into and out of communication with the ports I19. I

In operation, the valve member I14 normally occupies the position, shownin Fig. 7, in which the roove I8I is closed, and the tapered grooves I93are out of communication with the port W9. At this time, no fluid passesthrough the valve I68, and the cylinder I is relieved through I61-I18-I80I82I88-I13 ,I12 to the reservoir 4. Upon feed movement of thequill I0 into the forward end position against the positive stop, thespindle 9 will of course come to a stop, and upon the cessation ofmotion, thepi'essure in the pump control line 93 will drop, therebycausing an increase in the pump displacement. Since the delivery fluidhas no place to go, the pump pressure will rise. The rising pressure,acting on 1 the pressure face I92, will ultimately shift the valveplunger I14 to move the groove I82 out of communication with the portsI80, and the groove I8I' into communication therewith. Thereupon, a flowconnection is established to the cylinder I65 from the pump 53 through55-I11-I19 I86-I88-I84-I89I8I-I80--I18 and I61. The transmitted pressureacts on the piston I64 to move the latter at a graduated rate dependingon the flow rate through the orifice I88. It

J5 will be understood that the elevated pressure,

These grooves are con- 6 l3. which acts on the plunger 8| serves to.reduce the pump displacement, and hence the orifice 199 sets up apressure difierential influencing the .volume output of the pump and thesupply of ward-end of thecutting feed movement. As soon as the valve56is near the stop position, the

spring-actuated plungers I53 and I54 will' act I to complete rotationthereof quickly into reverse position.

The pressure rise during the dwell period is limited to a predeterminedmaximum. Should the pump pressure rise to this maximum, which isdetermined by the pressure of the spring I16,

it will move the valve plunger I14 sufliciently to open the taperedgrooves I93 to the ports I19, and thereby cause excess fluid to berelieved through the relief valve passage I90 to the drain line I12. Inthis condition, the valve I68 will act both as a dwell return and arelief valve. Thus, for the longer dwell periods, the relief of excessfluid serves to maintain the pump delivery pressure substantiallyconstant, and the orifice I88 passes fluid entirely under pressurecontrol to meter the supply to the cylinder I65-at a rate determined bythe orifice flow characteristics. 1

Optional means is provided for actuating the control valve 56 by remotecontrol. When the remote control is not utilized, the hollow plunger I59is open at both ends so as to be pressure balanced for free manualoperation of the valve 56 bymeans of the hand knob I30. When the,

remote control is desired, the plunger I59 is closed by threading a plugI94 (Fig. 5) into one end. Two fluid lines I95 and I96 open to oppositeends of the bore I60, and are adapted to be connected by a remotecontrol pilot valve I91 to exhaust or selectively to pressure.

The valve I91 comprises a valve housing I98 mounted on a suitablesupport, such as a plate I99 attached to some part of the machine frame(not shown) on which the power unit is used.

Formed in the housing I98 is a valve bore 200 having longitudinallyspaced port connection with the pump branch pressure line 85, theexhaust line 59 and the remote control lines I95 and I96.

14 plunger 20I. In the'neutral position, the valve plunger 20 I connectsboth lines I95 and I96 to the exhaust line 59 and blocks the'pressureline 85 sothat the remote control plunger I59 is pressure balanced topermit free adjustment of the valve 56 by the dogs Ill, I42 and l43 orby operating of the hand knob I30.

Upon energization of the solenoid 203, for ex ample at any time desiredor in case of emergency during the forward translation of .the quill I0,the plunger will be shifted to connect the remote reverse line I96 topressure and the line I95 to exhaust. 56 will be shifted into reverseposition. Thereupon, the spring 205 again returns the valve member 20!to neutral. movement of the quill I0, the stop dog I moves the valve 56into stop position and maintains it there until the next cycle isinitiated by again energizing the solenoid 202.

It will be noted that the hydraulic power unit is subject to manualcontrol, either by means of the hand knob I or the remote control at anypoint within the limit of the automatic range without likelihood ofinjury to the structure. The unit is compact and sturdy, and can beoperated at a relatively high fluid pressure without creatingobjectionable heating since no excess fluid required to be dischargedthrough a relief valve is normally delivered by the pump.- Any leakagein the hydraulic system is automatically com.- pensated for sincetheorifice control will reflect such leakage and adjust the pumpdisplacement accordingly. By using a suitable pump control pressure inthe low-compressibility range of the fluid and by compensating for anyleakage, a uniform rate of feed movement is obtained regardless of loadvariations.

It is to be understood that while the invention has been shown asincorppralledvin a hydraulic power unit of the quill type, variousfeatures thereof are also applicable to hydraulic power units of thesliding head type.

-In instances where a comparatively high control pressure is desired, itmay be advantageous v to provide a modified pump control line 93a hav- Avalve plunger 20I of the spool type is slidably adjustable in the bore200. v

The valve plunger 20I may be adjustable by any suitable means, and inthe present instance two solenoids 202 and 203 controlled by electricpush buttons (not shown) are mounted'on the support I99 and have coresor armatures 204 connected respectively to opposite ends of the plunger.

Upon energization of the solenoid 202, the plunger 20I will be shiftedin a direction (Fig.

10) to connect the remote start line I95 to pres- I sure and the lineI96 to exhaust. Thereupon, the pressure fluid acting on the remotecontrol plunger I59 will shift the control valve 56 from the stopposition into the rapid approach or starting position. As soon as thisadjustment is effected, I

the push button is released to deenergize the solenoid. A coiledcompression spring 205, inter-' posed between the valve plunger 20I anda bracket 206 on the support, then returns the plungerto intermediateneutral position. Expansion of the spring 205 is limited by abutmentwith the housing I98 to prevent over travel past neutral of the inginterposed therein a check valve 201 permitting free flow to the controlplunger 02, and a parallel flow restriction 209 for dampening the flowof fluid from the plunger. Such optional construction is indicated'inFig, 10a, the. modified line 93a being used in lieu-of the line 93 in-Fig. 10.

The pump 53 per se is covered in my copending divisional application,Serial No. 710,153, filed November 15, 1946.

I claim as my invention:

1. A hydraulic power unit comprising, in comblnation, a hydraulic motor,a variable delivery pump having an adjustable member for controlling thepump displacement, spring means in said pump acting on said member in adirection to increase the displacement of said pump, means for drivingsaid pump, an exhaust line, hydraulic means for counterbalancing saidmember against the pump reaction, hydraulic means acting on said memberin a direction to decrease the displacement of said pump, and a controlvalve,

adapted in one positionjto connect said pump and exhaust line toopposite sidesof said motor and being adjustable into a stopposition toblock the forward side of said motor, toconnect the other side of saidmotor to said exhaust line, and to connect-the outlet of said pump tothe last As a result the control valve At the end of the returnmentioned hydraulic means whereby to adjust Y said pump into position ofzero displacement;

2. Ahydraulic power unit comprising, in combination, a piston andcylinder motor, a variable delivery pump, means for driving said pump,said pump having an actuating member adjustable to vary the displacementfrom zero to maximum,,

means for counterbalancing said member against the pressure reaction insaid pump, valve means for connecting said pump reversibly to oppositeends of said motor, and for varying the resistance to flow oithe fluiddischarging from said cylinder for rapid traverse and feed operation.

andhydraulic means responsive to the pressure of the discharge end ofsaid motor for automatically adjusting the displacement of said pump toobtain maximum displacement during rapid traverse, and substantiallyconstant reduced displacement during feed operation.

3. A hydraulic power unit comprising, in combination, a cylinder, apiston slidably disposed in said cylinder, a variable delivery pump haveing a pressure discharge line, means for driving said pump, an exhaustline, adjustable valve 1 means for connecting said discharge line andsaid exhaust line selectively to opposite ends of said cylinder totranslate said piston at rapid traverse and feed rates, orifice meansconnected to receive fluid discharging from said cylinder during feedoperation, and means responsive to the pressure at the inlet side ofsaid orifice means for controlling the displacement of said pump tomaintain a substantially constant rate of fluid flow through saidorifice under varying load conditions during feed operation.

4. A hydraulic power unit comprising, in combination, a cylinder, apiston slidably disposed in said cylinder, a variable delivery pumphaving a pressure discharge line, means for driving.

said pump, an exhaust line, adjustable valve means for connecting saiddischarge line and said exhaust line selectively to opposite ends ofsaid cylinder to translate said piston at ripid traverse and feed rates,orifice means selectively available under the control of said valvemeans for setting controlling the pump displacement,spring means in saidpump acting on said member in a direc tion to increase the displacementof said pump;

means for driving said pump, an exhaust line,hydraulic means forcounterbalancing said member against the pump reaction, hydraulic meansacting on said member-in a direction to decrease the displacement ofsaid pump and responsive to the pressure in said exhaust line exerted inopposition to said spring means, and a control valve adapted in oneposition to connect said pump and spring means in said pump acting onsaid member up a back pressure in said exhaust line during feedoperation, and means responsive to the pressure at the discharge side ofsaid cylinder for controlling the displacement of said pump.

5. A hydraulic power unit comprising, in combination, a cylinder, apiston reciprocable in said cylinder, a translatable element connectedwith said piston, a drive shaft, a variable delivery pump driven by saidshaft and having an adjustable element for controlling the pumpdisplacement, supply lines opening to opposite ends of said cylinder, anexhaust line having a restricted adjustable oriflce control passage anda parallel less restricted passage, pressure responsive means operableto shift said adjustable element respectively in response to an increaseor decrease-in pressure in said exhaust 'line to decrease or increasesaidpump displacement, a rotary control valve for connecting said supplylines selectively to said pump and to said passages and said pressureresponsive means selectively to said passages whereby to translate saidfirst-mentioned element selectively at a rapid approach, 'forward feedor rapid return, and means controlled by the translation of saidfirst-mentioned element for auto matically adjusting said valve.

6. A hydraulic power unit comprising, in combination' with atranslatable element, a hydraulic motor for translating said element, avariable delivery pump having an adjustable member for in a direction toincrease the displacement of said pump, means for driving said pump, anexhaust line, hydraulic means for counterbalancing said member againstthe pump reaction, hydraulic means acting on said member in a directionto decrease the displacement of said pump and responsive to the pressurein said exhaust line exerted in opposition to said spring means", and acontrol valve adapted in one position to connect said pump in parallelto opposite sides of said motor and to connect second mentionedhydraulic means to said exhaust line to effect adjustment of said memberinto position for maximum pump displacement, and being adjustable intoanother position to connect one end of said motor to said pump and theother end of said motor to said exhaust line, and to interpose a flowrestriction in said exhaust line to adjust said member into position forreduced pump displacement.

8. A hydraulic transmission for a reversibly movable machine toolelement comprising, in combination, a-hydraulic motorior translatingsaid element, supply lines opening to opposite sides of said motor, avariable delivery pump having a pressure discharge line and anadjustable control membermovable to vary the pump displacement through arange from zero to maximum, spring means acting on said member in adirection to increase said pump displacement,

means responsive to the discharge pressure of said pump forsubstantially counterbalancing said member against the pumping reaction,an exhaust line, acontrol valve adjustable into position to connect saidsupply lines respectively to said discharge and exhaust lines to eilectmovement of said element in one direction, stop means for positivelylimiting the movement of said element said member with said .stop meansto adjust said valve out of said position.

9. A hydraulic transmission renal reversibly movable machine toolelement comprising, in

combination, a hydraulic motor for translating said element, supplylines opening to opposite mum, spring means acting on said member in adirection to increase said pump displacement, means responsive to thedischarge pressure of said pump for substantially counter balancin saidmember against the pumping reaction, an exhaust line, a control valveadjustable into position to connect said supply linesrespectively tosaid discharge and exhaust lines to eflect movement of said element inone direction, stop means for positively limiting the movement of saidelement in said one direction, a restricted flow orifice functionallyinterposed to receive fluid discharging from said motor through saidexhaust line when said element is moving in said one direction, meansincluding a hydraulic actuator acting on said member in opposition tosaid spring means and responsive through-a control line to adjust saidmember to decrease the pump displacement upon an increase in thepressure at the inlet side of said orifice and to increase saiddisplacement upon a decrease in the pressure at. the inlet side of saidorifice, said valve being adjustable into a second position to reversethe connections of said supply lines to said discharge and exhaust linesand thereby to 'efiect movement of said element in the reversedirection, and means including a hydraulic actuato'r automaticallyoperable in response to a predetermined pressure rise in said dischargeline upon engagement of said element with said stop means to adjust saidvalve into said second position after a predetermined dwell period ofsaid element.

10. A hydraulic tra'nsmission for a reversibly movable machine toolelement comprising, in combination, a hydraulic motor for translatingsaid element, supply lines opening to opposite sides of said motor, avariable delivery pump hava ing a pressure discharge line and anadjustable control member movable to vary the pumpdisplacement through arange from zero to maximum, spring means acting on said member in adirection to increase said pump displacement, means responsive to thedischarge pressure of said pump for'substantially counter balancing saidmember against the pumping reaction, an exhaust line, a control valveadjustable into position to connect said supply lines respectively tosaid discharge and exhaust lines to effect movement of said element inone direction, stop means said supply lines reversiblyto said deliveryand exhaust lines, a hydraulic valve motor having a reciproca ry plimcerextending transversely of said valveand geared thereto, automatic meansfor adjusting said valve in'timed relation to the movement of saidelement, a remote control pilot valve normally in intermediateneutralposition to connect opposite ends of said valve motor to said exhaustline, and being-adjustable oppositely out of said neutral position toconnect said delivery and exhaust lines reversibly to opposite ends ofsaid valve motor, and manually controlled means for selectivelyadjusting said pilot valve at any time within the range of control oisaid automaticmeans. V

12. A hydraulic transmission for a reversibly movable machine toolelement comprising, in combination, a hydraulic motor for translatingsaid element, supply lines opening to opposite sides of said motor, apump having a delivery line, an exhaust line, a rotary control valveadjustable into opposite limit positions to connect said supply linesreversibly to said delivery and exhaust lines, a hollow plungerreciprocable transversely of said valve and operatively geared to saidvalve, means for automatically adjusting said valve in timed relationtothe movement of said element, and a hydraulic actuator for shiftingsaid plunger. a

13. A hydraulic transmission for a reversibly movable machine toolelement comprising, in

, combination, a hydraulic motor for translating haust lines, ahydraulic valve motor having a for positively limiting the movement ofsaid element in said one direction, means including a hydraulic actuatoracting on said member in opposition to said spring means and operable inresponse to "the pressure in said exhaust line to efiect an increase inpump displacement upon a decrease in the exhaust pressure and a decreasein pump displacement upon an increase in the exhaust pressure, saidvalve being further adjustable tovary the back pressure in said exhaustline whereby to effect adjustment of said pump control member.

ll. A hydraulic transmission for a reversibly movable machine toolelement comprising, in combination, a hydraulic motor for translatingsaid element, supply lines opening to opposite sides of said motor, apump having a delivery line, an exhaust line, a rotary control valveadjustable into opposite limit positions to connect said element, supplylines opening to opposite sides of said motor, a pump having a deliveryline, an exhaust line, a rotary control valve adjustable into oppositelimit positions to connect said supply lines reversibly to said deliveryand exreciprocatory hollow plunger extending transversely of said valveand geared thereto, automatic means for adjusting said valve in timedrelation to the movement of said element, a ,re-' mote control pilotvalve normally in intermediate neutral position to connect opposite endsof said valve motor to said exhaust line, and being adjustableoppositely out of said neutral position to'connect said delivery andexhaust lines reversibly to opposite ends of said valve motor, manuallycontrolled means for selectively adjusting said pilot valve at any timewithin the range of control of said automatic means, and hydraulic dwellmeans for shifting said plunger when said pilot valve is in neutralposition.

'14. A hydraulic transmission for a reversibly movable. machine toolelement comprising, in

combination, a hydraulic motor for translating a direction to increasesaid pump displacement,

means responsive to the discharge pressure of said pump forsubstantially counter balancing said member against the pumpingreaction, an exhaust line, a control valve adjustable into position toconnect said supply lines respectively to said discharge and exhaustlines to efiect movement of said element in one direction, stop meansfor positively limiting the movement of said element in said onedirection, hydraulic meansineluding a plunger acting on said member inopposition to said spring means in a direction to decrease the pumpdisplacement'and having a pressure control line adapted for connectionto said 20 increase the displacement "of said pump, means for drivingsaid pump, hydraulic means for counterbalancing said member against thehydraulic bination with a translatable element, a hydraulic *motor forreversibly translating said element, a delivery pump having a pressuredischarge line,-

,a direction valve for connecting said line reversibly to opposite sidesof said motor, means itor positively limiting the movement of saidelement in one direction, a hydraulic actuator for reversing said valvetov efiect movement of said element in the'other direction and having aipressure control line, and a dwell and, relief valve operable byapredetermined rise in pressure in said discharge line upon engagement ofsaid element with said means to relieve said discharge line fordiversion of excess fluid andto connect a said discharge line through anoriflce to said control line whereby to effect a delayed reversal ;ofsaid direction valve by said actuator.

16. A hydraulic power unit, comprising, in combination with atranslatable element, a hydraulic motor for reversibly translating saidelement, a

delivery pump having a pressure discharge line, a direction valve forconnecting said line re- I :versibly to opposite sides of said motor,means for positively limiting th movement of said element in onedirection, a hydraulic actuator for reversing said valve to effectmovement of said element in the other direction, and having a pressurecontrol line, a dwell valve normally conditioned to connect said controlline to exhaust and being operable by a predetermined rise in pressurein said discharge line upon engagement of said element with said meansto connect said discharge line through a flow rectriction to saidcontrol line, and means normally closed during the translation of saidelement and operative to relieve excess fluid from said discharg line tolimit said pressure rise to a substantially constant maximum, whereby toeflect a delayed reversal of said direction valve by said actuator.

17. A hydraulic power unit, comprising, in comreaction of said pump,hydraulic means acting on said member in a direction to decrease thedisplacement of said pump, and control valve means selectivelyadjustable to direct fluid from said pump to said motor to effectoperation of said motor, or to connect said pump to said last-mentionedhydraulic means wherebyito adjust said pump into position ofsubstantially zero displace-- ment.

19. A hydraulic power unit comprising, in combination, a reversiblehydraulic motor, a variable delivery pump, means for driving said'pump,said pump having an actuating member adjustable to vary the displacementfrom zero to maximum, means for counterbalancing said member against thehydraulic pressure reaction in said pump, an exhaust line including apassage with a flow restriction and a less restricted passage about saidrestriction, and valve means for connecting said pump reversibly toopposite ends of said motor bination with a translatable element, ahydraulic motor for reversibly translating said element, a delivery pumphaving a pressure discharge line, a, direction valve for connecting saidline resersibly to opposite sides of said motor, means ior positivelylimiting the movement of said element in one direction, a hydraulicactuator for reversing said valve to eifect movement of said element inthe other direction, and having a pressure control line, a dwell valvenormally conditioned to connect, said control line to exhaust and beingoperableby a predetermined rise in pressure in said discharge line uponengagement of said element with said means to connect said dischargeline through a flow restriction tosaid control line, means normallyclosed during the translation of said element and operative to relieveexcess fluid from said discharge line to limit said pressure rise to asubstantially constant maximum, whereby to effect a delayed reversal ofsaid direction valve by said actuator,- and a pilot valve operableindependently of said actuator to eflect reversal oisaid directionvalve;

and for directing fluid discharging from said motor to said exhaust lineselectively through said first named passage or through said lessrestricted passage about said restriction respectively for feed andrapid traverse "operation, and pressure 1 responsive means selectivelyconnectible by said valve means to said exhaust line ahead of saidrestriction for automatically adjusting said memher to adjust thedisplacement of said pump tov obtain respectively maximum displacementdur'- ing rapid traverse, and substantially constant, reduceddisplacement during feed operation.

, 20. A hydraulic transmission for a reversibly movable machine toolelement comprising, in

combination, ahydraulic motor for translating said element, supply linesopening to opposite sides of said motor, a pump having a delivery line,an exhaust line,'a rotary control valve adjustable into opposite limitpositions to connect said supply lines reversibly to said delivery andexhaust lines, a plunger reciprocable transversely of said valve andoperatively geared to said valve, means for automatically adjusting saidvalve in timed relation to the movement of said element, a hydraulicvactuator having a control line and a piston movable in response to thesupply of pressure fluid through said control line out of idle positioninto end engagement with said plunger to move said plunger from theadjacent end position into an intermediate position, load and firemechanism operable upon movement of said plunger into said intermediateposition to continue movement thereof into the opposite end position,and means automatically operable upon a predetermined rise in pressure,in said delivery line to supply fluid under pressure at agraduated rateto said control line.

21. A hydraulic transmission for a reversibly movable machine toolelement comprising, in combination, a hydraulic motor for translatingsaid element, supply-linesopening to opposite sides of said motor, apump having a delivery line, an exhaust line, a rotary control valveadjustable into opposite limit positions to connect said supply linesreversibly to said delivery-and i 18. A hydraulic power unit comprising,in com- 3 ling the pump displacement, spring means in said pump actingon said member in a direction to.

exhaust lines,'a plunger reciprocable transversely of said valve-andoperatively geared to said valve, means for automatically adjusting saidvalve in timed relation to the movement or said element, a

hydraulic actuatorhaving a control line and a piston movable in responseto the supply oi. pressure fluid through said control line out of idle21 position into end engagement with said plunger to shift'the latter,and means automatically operable upon a predetermined rise in pressurein said delivery line to supply fluid under pressure at a graduated rateto said control line,

22. A hydraulic power unit comprising, in com- 7 exhaust line, andcontrol valve means having different selective conditions of adjustment,in one of which said pump is connected to opposite sides of said motorand said second hydraulic means is connected to said exhaust line, inanother of which said pump is connected to one side 01' reduced pressurearea of said motor and the other side of said motor and said secondhydraulic means are connected to said exhaust line, in another of whichsaid pump is connected to said other side of said motor and said onesideof said motor and said second hydraulic means are connected to saidexhaust line in advance of said fiow restriction, and in another ofwhich said one side of said motor is blocked and said other side of saidmotor is connected to said exhaust line and said pump-is connected tosaid second hydraulic means. MAX A. MAT-HYS.

REFERENCES CITED The following references are of record 'in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,521,884 Higgins Jan. 6, 19252,129,828 Dunn Sept. 13, 1938 1,974,137 I Ferris Sept. 18, 19342,005,018 West et a1 June 18, 1935 2,160,217 Kingsbury May 30, 19391,996,466 Ernst Apr. 2, 1935 2,001,059 Ferris May 14, 1935 2,238,061Kendrick Apr. 15, 1941 2,130,393 Johnson Sept. 20, 1938 1,838,028 Ernstet al. Dec. 22, 1931 1,893,076, Flygare Jan. 3, 1933 1,943,061 DouglasJan. 9, 1934- 1,952,690 Strom Mar. 27, 1934 1,969,063 Ernst etal. Aug.7, 1934 1,978,346 Ernst et al. -11 Oct. 23, 1934 2,000,553 Alden May 7,1935 2,071,677 Wood Feb. 23, 1937 2,269,697 Silven Jan. 13, 19422,030,888 Morgan Feb. 18, 1936 2,063,414 Tweddell Dec, 8, 1936 2,110,393Edwards Mar. 8, 1938 2,056,896

Douglas Oct. 6, 1938

